Electric arc heating unit with electrode matrix



NOV. 1970 A. HOFFMAN ErAL 3,542,930

ELECTRIC ARC HEATING UNIT WITH ELECTRODE MATRIX Fild July 22, 1968 3 Sheets-Sheet 1 NOV. 24, 1970 HOFFMAN ETAL 3,542,930

ELECTRIC ARC HEATING UNIT WITH ELECTRODE MATRIX Filed July 22, 1968 3 Sheets-Sheet 2 24, 1970 A. HOFFMAN ETAL 3,542,930

ELECTRIC ARC HEATING UNIT WITH ELECTRODE MATRIX Filed July 22, 1968 3 Sheets-Sheet 5 /6'4 I60 64 A 50 /54- /60 54 M0 A'rm/mIcYS United States Patent O 3,542,930 ELECTRIC ARC HEATING UNIT WITH ELECTRODE MATRIX Allen Hoffman, Philadelphia, Pa., and Peppino N. Vlannes, Fairfax, Va., assignors to Vapo-Waste, Inc., Dover, Del., a corporation of Delaware Filed July 22, 1968, Ser. No. 746,348 Int. Cl. Hb 7/18 US. Cl. 13-9 14 Claims ABSTRACT OF THE DISCLOSURE An arc heating unit comprising a large plurality of electrodes arranged in rows and columns to form a matrix. The electrodes of the matrix are fired according to a desired pattern, to effect a mattress of arcs or flame capable of producing high temperatures over a large surface area or within a large column.

BACKGROUND OF THE INVENTION The present invention relates to an electric are heating unit featuring a unique arrangement of a large number of electrodes which, when fired, will create a mattress of arcs or flame capable of producing very high temperatures over a large area or volume.

The use of electric arcs to generate heat within a furnace or oven is not new. However, normally only two electrodes are utilized, with the result that the heat source is very localized, and frequently is incapable of creating a desired temperature over the area or volume desired.

The desirability of using electric arc heating for furnaces is increasing as technology demands the high temperatures and the fine temperature control obtainable with such units, and as electric power in sufiicient quantity is increasingly made economically available. In addition, the air pollution problems associated with the use of coal and other commonly used heat sources are causing many industries to look toward electric heating. However, there has been a need for an arc unit capable of providing desired high temperatures over the large areas required in such applications as the commercial melting of large amounts of metal and the burning of refuse, a need which the present invention satisfies.

SUMMARY OF THE INVENTION The electric arc heating unit of the present invention is capable of producing a mattress of arcs or flames extending over a large area, which thus makes possible the heating of a large volume or an enlarged surface area, uniformly to a desired temperature. The unit essentially consists of a large plurality of electrodes, mounted in rows and columns to form a matrix. The electrode matrix can be of nearly any desired length and breadth, and the electrodes thereof are connected with a power source so they can be fired according to a desired pattern.

The electrode matrix can be mounted in a furnace or elsewhere, and \usually a plurality of units is utilized to provide even heat of the desired temperature. The invention contemplates several arrangements for transmitting power to the electrodes, which make possible many different firing patterns. For example, in different embodiments of the invention the electrodes are fired simultaneously, in order at random, or in rotation, depending upon the results desired and the structure employed.

The invention also contemplates the use of one or more electrode matrix units to generate heat within a rotating furnace or oven. In this instance, the electrodes are supplied with brushes that are engageable with a comice mutator. Several forms for the electrode tips are also presented, each having operational advantages.

It is the principal object of the present invention to provide an arrangement of electrodes capable of producing a mattress of arcs or flame, for use as a heating unit in a furnace or the like.

Another object is to provide an arc heating unit that utilizes a plurality of electrodes arranged in a matrix, which electrode matrix can be energized in different ways to provide a plurality of arc patterns.

A further object is to provide an electrode matrix heating unit designed for use with a rotating furnace or oven.

Still another object is to provide a variety of conductor arrangements for transmitting energy to an electrode matrix.

Yet another object is to provide a variety of tip configurations for use with the electrode matrix of the invention.

Other objects and advantages of the invention will become readily apparent from the following description of the preferred embodiments, when taken in conjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary side elevational view of a rotatable drum furnace having three of the present electric arc heating units mounted therein, and in particular shows the spacing between the electrodes of each column, and the wider spacing between each pair of columns;

FIG. 2 is a vertical section taken on the line 2-2 in FIG. 1, showing in particular the brush and commutator arrangement for firing each electrode matrix in turn as the drum is rotating;

FIG. 3 is a side elevational view of a cylindrical furnace for melting metals and other materials utilizing four electrode matrix units, wherein all of the electrodes of each electrode matrix are fired simultaneously.

FIG. 4 is a vertical section taken on the line 4-4 of FIG. 3, showing the internal construction of the cylindrical furnace;

FIG. 5 is a diagrammatic view showing an electrode matrix wherein the electrodes are arranged in equally spaced columns, and showing a bus bar network that is relatively moveable along the electrode columns to effect progressive firing of all of the electrodes composing the matrix;

FIG. 6 is a diagrammatic view showing an electrode matrix identical to that of FIG. 5, but with a modified bus bar network that is designed to energize the electrodes of each pair of columns with alternating polarity as it is moved relatively along said columns;

FIG. 7 is a diagrammatic view showing another form of relatively moveable bus bar network, which can be used with electrode matrix units such as those shown with the cylindrical furnace of FIG. 3 to effect progressive firing of the electrodes longitudinally of the furnace;

FIG. 8 is a diagrammatic view of a criss-cross bus bar network, which is designed for easy connection of the electrodes of an electrode matrix in any desired polarity pattern;

FIG. 9 is a perspective view of a pair of electrode tips for confining the arc to a single location, designed particularly for use with the electrode matrix of FIG. 1;

FIG. 10 is a perspective view of a pair of electrode tips for use in an electrode matrix such as that of FIGS. 5-8, designed to are in any direction across the rows or along the columns of the electrode matrix; and

FIG. 11 is a perspective view of another pair of multidimensional electrode tips, particularly designed with a large rounded surface for long life.

3 DESCRIPTION OF THE PREFERRED EMBODIMENTS The electric arc heating unit of the invention has many possible applications, only two of which are a thermal decomposition furnace for refuse and a metallurgical furnace. Such a refuse furnace utilizing the present arc unit is shown in FIGS. 1 and 2, and such a metallurgical furnace is shown in FIGS. 3 and 4. See also the more detailed disclosure of refuse handling apparatus in our application, Ser. No. 746,331 filed concurrently herewith.

Referring now to FIGS. 1 and 2, a rotatable cylindrical drum furnace 2 is mounted on rollers 4 connected to the confronting channel members 6 of the base 8, the drum furnace 2 having a large gear 10 secured to the front wall 12 thereof which is engaged with a drive gear 14 mounted on the output shaft of a motor 16, secured to the base 8. The motor 16, acting through the gears 10 and 14, is thus arranged to rotate the drum furnace 2 about its central axis. An upright frame 18 is secured to the base 8, and includes a cross beam 20 to which a bearing unit 22 is attached. The bearing unit 22 receives a shaft 24 carried by the hub of the gear 10, which stabilizes the revolving drum 2.

The rotating drum 2 is designed to withstand high temperatures, and high pressures and to this end the cylindrical wall and the front end wall 12 thereof comprise inner and outer shells 26 and 28, respectively, having insulation 30 disposed therebetween. Typically the inner shell 26 and the outer shell 28 would be made of- Type 304 stainless steel and Type 1020 steel, respectively, and the insulation 30 would be a material such as Marinite manufactured by the Johns-Manville Corporation. The drum 2 is loaded through a loading door 32 at its rear end, the door 32 being mounted by suitable hinge structure 34 and incorporating suitable latch means (not shown), operated by handles 36. The loading door 34 is preferably constructed in the same double-wall manner as the walls of the drum 2.

The ash and other residue remaining after completion of a thermal decomposition cycle is removed from the drum furnace 2 through an opening 38 in the sidewall thereof, the opening 38 being closed by a specially shaped emptying door 40 when the furnace is in operation. The door 40 is opened by being moved upwardly into the furnace, and includes a peripheral rim 42 that engages the edge of the opening 38 when the door is closed. Conventional locking structure (not shown) is utilized to secure the emptying door 40 in place while the drum furnace is in operation, and the door has a wedge-shaped 'or gable roof-like upper surface 44 that causes ash material to slide thereoff during the emptying process.

Heat is supplied to the drum furnace 2 by three electric arc units 46, each constructed according to the present invention. Each of the arc units 46 includes an electrode matrix M, comprised of sixty-four electrodes 48 arranged in eight circumferentially extending columns, and eight axially extending rows. Each of the electrodes 48 is mounted to extend through an opening 50 in the sidewall of the drum 2, and is insulated from the drum 2 by ball and socket ceramic beads 52 coated and bonded in place with Thermon Grade T-3 heat transfer cement, or an equivalent material. Each of the electrodes 48 terminates at its outer end in an electrically conductive contact or brush 54.

The electrodes 48 of the matrix M of each unit 46 are designed to fire in generally axial paths adjacent the interior surface of the drum furnace. To this end, the eight columns of electrodes are arranged to form four pairs of columns 56, 58, 60 and 62, with the tips of the electrodes 48 of each column pair being spaced to ensure firing or arcing therebetween when the unit is operated at design voltage. The pairs of columns 56, 58, 60 and 62, on the other hand, are spaced apart further than are the columns of each pair, a distance sufficient to prevent arcing between electrodes of adjacent column pairs.

The tips of the electrodes 48 can be of any suitable design, and are preferably carbon tipped. However, a tip configuration especially designed for producing the desired axial firing between pairs of electrodes 48 in each pair of columns 56, 58, 60, and 62 is shown in FIG. 9. In FIG. 9 each of the electrodes 48 has a tip portion 64 that extends at a right angle from the body thereof, each tip portion 64 terminating in a blunted, conical firing tip 66. The tip portions 64 of adjacent electrodes 48 in each column pair face each other, and define a spark gap therebetween.

The electrodes 48 are supplied with current through a commutator assembly 68 mounted above the drum furnace 2, and carried by the vertical frame 18. The commutator assembly 68 includes an arcuate mounting plate 70, to the undersurface of which arcuate bus bars 72, 74, 76, 78, 80, 82, 84 and 86 are secured and insulated from each other. The bus bars 72 and 74 are associated with electrode column 56, the bus bars 76 and 78 with electrode column 58, and so on. All of the bus bars 72, 76, 80 and 84 are interconnected and are connected to a positive power terminal, and all of the bus bars 74, 78, 82 and 86 are interconnected and are connected to a negative power terminal, power being supplied through a cable 88 from a suitable A.C.-D.C. converter unit or other source of direct current (not shown). Obviously, the polarity of the sets of bus bars can be reversed, if desired.

In use the drum furnace 2 is first loaded with refuse through the loading door 32, which is then closed and secured. The drum 2 is then placed in rotation by the motor 16, whereby the electrode contacts or brushes 54 of each arc unit 46 are brought into engagement with their respective bus bars 72 through 86 of the commutator assembly 68.

As each electrode matrix M is rotated into engagement with the commutator unit 68 the electrodes 48 across each row of the matrix will be fired sequentially, and arcs will be formed between each axially adjacent pair of electrodes in each column pair. The result will be the creation of a mattress of arcs or flame, which will be effective to create a very high temperature within the drum furnace 2. The heat of the arc mattress can be controlled by the amount of current supplied to the matrix M. For refuse combustion, a typical power requirement for the sixtyfour electrode matrix M would be a current of about amperes, at about 50 0 volts.

The three arc units 46 will be fired in sequence as the drum furnace 2 rotates. Obviously, more or less arc units 46 can be utilized, if desired. In addition, the commutator arrangement 68 can be of various arc lengths to vary the firing time of each electrode matrix, and indeed additional commutators can be employed if desired.

When combustion of the refuse is completed the drum furnace 2 is stopped from rotating, to rest generally as shown in FIG. 2. The door 40 is then opened to remove the ash and other remains.

Turning now to FIGS. 3 and 4, a metallurgical furnace for continuous melting of material supplied thereto is shown at 90, and includes a cylindrical furnace chamber 92 comprised of upper and lower semi-cylindrical sec tions 94 and 96, joined along one edge by hinges 98. The sections 94 and 96 are of double-wall construction similar to the drum furnace of FIGS. 1 and 2, and are held in closed position by bolts 100 passed through confronting flanges 102 and 104 mounted thereon, respectively. An open trough 106 of heat-resistant material extends completely through the cylindrical furnace chamber 90, and is supported therewithin by brackets 108 attached to the lower section 96.

The metallurgical furnace 90 is equipped with four identically constructed arc units 108, each comprised of sixty-four electrodes 110 mounted in a block 112 to form a matrix M of columns and rows. The electrodes 10 extend outwardly through bores 114 in the walls of the furnace chamber 94, and are insulated therefrom and from each other by insulators 116.

The electrodes 110 of each matrix M are arranged in axially extending pairs of columns 118, 120, 122 and 124, with the spacing between electrodes of each column pair being selected to provide a proper are for the designed current and voltage. As in FIGS. 1 and 2, the column pairs are spaced further apart than the electrodes in the columns, to prevent arcing therebetween.

The electric arc units 108 are intended to be operated so that all of the electrodes 110 of each unit are fired simultaneously, to provide a large mattress of arcs or flame. To accomplish this, rectangular blocks 126 of insulative material are mounted on the exterior of the furnace chamber 92 by support posts 128 above each electrode matrix M, the blocks 126 mounted on the lower chamber section 96 having brackets 130 connected thereto for supporting the cylindrical furnace. Each of the insulative blocks 126 has a bus bar network mounted thereon, comprises of four bus bars 132 connected by a cross bus bar 134 to supply current of one polarity, e.g. positive, to the electrodes 110 of one column of each column pair 118, 120, 122 and 124, and a second set of four bus bars 136 connected by a cross bus bar 138 to supply current of the opposite polarity to the remaining electrodes 110.

To place the cylindrical furnace 90 in operation the cross bus bars 134 and 138 for each matrix M are connected by leads 140 and 142, respectively, to a source of direct current, whereby all of the electrodes 110 of the matrix are fired to create an arc mattress. All of the electric are units 108 can be fired at the same time, or if desired they can be fired in any sequence by the use of conventional switching circuits (not shown). When the cylindrical furnace 90 has reached the desired temperature, solid metal is fed thereinto from one end in the trough 106. The metal is melted within the chamber 92, and then flows in a liquid state through the trough from the other end of the furnace, the trough 106 preferably being slight 1y inclined to aid such flow.

While two types of furnaces utilizing electric arc units constructed according to the electrode matrix concept of the invention have been described, it is obvious that this concept can be adapted to many other applications. Further, while an electrode matrix consisting of sixty-four electrodes arranged in four column pairs has been described, both the number of electrodes and their spacing within the matrix can be varied. In addition, various bus bar networks can be utilized for supplying current to the electrode matrix, to obtain different firing patterns.

Referring now to the diagrammatic presentation of FIG. 5, an electrode matrix M" is shown incorporating electrodes 150 arranged in vertical columns and horizontal rows, with the same spacing between both the columns and the rows. Disposed over the electrode matrix M is a bus bar network 152, similar to that utilized in FIGS. 1 and 2 and which is mounted to be movable in the direction of the arrow relative to the electrode matrix. In practice, either the matrix M or the network 152 can be stationary, or both can be in motion but in opposite directions.

The network 152 includes a plurality of bus bar contact strips 154 connected to a common terminal bar 156, which in turn is connected to one pole terminal 158 of a power source, say the positive pole, and a second plurality of contact strips 160 connected to a terminal bar 162 and a negative pole terminal 164. The terminal bars 156 and 162 are of course normally elevated above their contact strips 154 and 160, or are otherwise arranged so that they will not contact the electrodes 150.

In operation, as the bus bar network 152 of FIG. 5, moves across the matrix M in the direction of the columns, arcs A will form between the horizontally opposed electrodes in adjacent columns. Because of equal spacing between the columns, as distinguished from the arrange- 6 ment of FIGS. 1 and 2, wherein the columns are arranged in pairs, arcs will be formed in FIG. 5 between each pair of electrodes across each row. Thus, when all of the electrodes 150 are energized the result will be a continuous mattress or blanket of high energy arcs, as indicated in FIG. 5 by the jagged lines A.

FIG. 6 shows another bus bar network that can be used with the electrode matrix M" of FIG. 5, designed to alternate the polarity of the electrodes 150. The network 170 comprises a first plurality of horizontally extending bus bars 172, connected to a common terminal bar 174 that is in turn connected to a positive power terminal 176, and a second plurality of horizontally extending bus bars 178 connected to a common terminal bar 180 and a negative power terminal 182. The bus bars 172 and 178 are all spaced above the electrodes 150, and contact strips 184 and 186, respectively, one for each column of electrodes 150, extend downwardly therefrom. The forward ends of the contact strips 184 and 186 are aligned, and said strips are arranged so that as the network 170 is moved along the columns of electrodes 150' each electrode will alternately be made positive or negative.

It should also be noted that even though the spacing between electrodes of the matrix M" of FIG. 6 is even, because of the arrangement of the contact strips 184 and 186 the electrodes 150 will be fired in column pairs as in FIGS. 1 and 2, with arcs A being formed only between every other pair of electrodes in a row as shown in FIG. 6. This is done by having the contact strips 184 and 186 arranged in positive pairs followed by negative pairs, as illustrated.

If the network 170 were to be modified to alternate the positive and negative contact strips 184 and 186, then an arc pattern like that of FIG. 5 would result. In FIG. 6 the arrow indicates that the matrix M" is moved relative to the network 170, but as has been explained, other types of relative motion are also possible.

FIG. 7 illustrates at 190 another type of bus bar network designed to be moved horizontally along the rows of electrodes 150 comprising the matrix M". The network 190 comprises a plurality of vertical contact strips 192 of one polarity, e.g. positive, alternated with a second plurality of contact strips 194 of the opposite polarity, the contact strips 192 and 194 being connected to terminal bars 196 and 198, respectively. It is seen that as the network 190 is moved relatively along the electrode rows, the electrode 150 in each column will successively be energized and de-energized, with alternating polarity.

FIG. -8 shows a criss-cross or mesh-like bus bar network 200 that is especially useful to permit easy connection of the electrodes 150 of the matrix M". The network 200 has a plurality of vertical bus bars 202 connected to a terminal bar 204, and a plurality of horizontal bus bars 206 connected to a terminal bar 208. The bars 202 are of course insulated from the bars 206, and the terminal bars 204 and 208 are connected to negative and positive power terminals 210 and 212 respectively.

The network 200 is positioned over the electrode matrix M", with one electrode 150 in each mesh opening. The electrodes 150 are then easily connected to either a positive or a negative bus bar, by whatever means is desired (not shown).

It has been mentioned that various electrode tip designs are usable with the invention, and specific reference has been had to the design of FIG. 9. FIG. 10 shows an electrode 48' with a cruciform tip formation thereon, whereby four cylindrical tips 220 extending at right angles are provided. This configuration is especially useful where different firing patterns are designed, as it can be fired in any of four directions. Another electrode tip, designed for firing in any direction and to have a 7 long life, is shown at 222 in FIG; 11. In this figure the tip 222 is generally spherical.

While the electric arc unit of the invention has been described with reference to use with direct current, it is to be understood that alternating current can also be employed. One particularly attractive result available with the use of alternating current is pulsed operation of the electrode matrix. Pulsed operation can be easily achieved utilizing conventional A.C. pulsing circuits, by anyone familiar with the principles of pulse operation.

It is, of course, to be understood that the forms of the invention shown and described herein are but preferred embodiments, and are not intended to be exhaustive of all possible variations and ramifications of the invention. For example, with respect to metallurgical furnaces alone it is contemplated that provision may be made for a controlled atmosphere of argon or the like. Also, various adaptations may be made to provide for use in more complex metallurgical processing. Thus, many further alterations and modifications are possible, all without departing from the present invention.

We claim:

1. An electric arc heating unit forfurnaces and the like, comprising a multiplicity of electrodes arranged in a multiplicity of parallel rows and a multiplicity of parallel columns, said columns extending at an angle to said rows to define an electrode matrix, each row and each column of said matrix having a multiplicity of electrodes therein, and each electrode of said matrix having an electrical contact on one end thereof and a tip on the other end, the tip of each electrode being sufiiciently close to the tip of at leastone other electrode of said matrix to produce an arc therebetween when energized to a specified voltage; and means engageable with said electrical contacts and operable for selectively energizing the electrodes of said matrix according to a desired pattern, to produce a selected array of arcs.

2. An electric arc heating unit as recited in claim 1, wherein said columns are arranged in pairs, the-tips of the electrodes in the columns of each of said pairs being spaced closely to produce an arc therebetween, and the electrodes of each pair of columns being spaced beyond arcing distance from the electrodes of adjacent pairs of columns.

3. An electric arc heating unit as recited in claim 1, wherein the electrodes of said columns and said rows are all equally spaced from each other.

4. An electric arc heating unit as recited in claim 1, wherein said electrodes are arranged in pairs, the tip of each electrode comprising a single projection extending generally normally from the body of saidelectrode, the projection on one electrode of each pair being directed toward and in general alignment with the like projection on the otherelectrode of said pair.

5. An electric arc heating unit as recited in claim 1, wherein each of said electrode tips is generally spherical.

6. An electric arc heating unit as recited in claim 1, wherein each of said electrode tips is cruciform shape.

7. An electric arc heating unit as recited in claim 1, wherein said energizing means includes: a power source; and a commutator assembly having mounted thereon a network of contact strips connected to said power source, said commutator assembly being mounted for motion relative to said electrode matrix, said contact strips successively engaging said electrical contacts of said electrodes when said commutator assembly is moved relatively to said electrode matrix to thereby effect sequential and selective firing of said electrodes, according to a predetermined pattern as set by the configuration of said contact strip network.

8 8. An electric arc heating unit as recited in claim 7, wherein the contact strips of said network are arranged to effect alternate energization and de-energization of said electrodes as said network is moved relative to said electrode matrix. 7

9. An electric arc heating unit as recited in claim 8,

wherein additionally said contact strips are arranged to reverse the polarity of each electrode for each successive energization.

10. In combination: a furnace, including Wall means defining a furnace chamber; at least one electric arc heating unit Within said furnace chamber and supported by said wall means, said unit comprising a multiplicity of electrodes extending through said wall means and arranged in a multiplicity of parallel columns and a multiplicity of parallel rows, said rows extending at an angle to said columns to form an electrode matrix, each column and each row of said matrix having a multiplicity of electrodes therein, the inner end of each electrode having a tip thereon and the outer end thereof bearing an electrical contact, and the tip of each electrode being spaced from at least one other electrode tip a distance effective to produce an arc therebetween when said electrodes are energized with opposite polarity; and means connectable with said electrical contacts for supplying electrical energy to the electrodes of said matrix, comprising: a power source; and a network of contact strips connected with said power source and engaged with said electrical contacts, whereby said electrodes are fired in a pattern determined by the configuration of said network to produce a preselected arc array within said furnace.

11. The combination as recited in claim 10, including additionally a commutator assembly mounted adjacent the wall means of said furnace and movable relatively thereto, said contact strip network being carried by said commutator assembly, whereby when said commutator assembly moves relatively to said wall means said contact strips successively engage said electrical contacts to effect sequential firing of said electrodes.

12. The combination as recited to claim 11, wherein said furnace is mounted for rotation about an axis pass ing through said furnace chamber, whereby to elfect relative motion between it and said commutator assembly.

13. The combination as recited in claim 12 wherein one of said contact strips is provided for each column of electrodes, said contact strips being arranged to effect successive firing of all of the electrodes in each row as said drum is rotated.

14. The combination as recited in claim 12, wherein said columns of electrodes are arranged in pairs, the electrodes of each column pair being spaced beyond arcing distance from the electrodes of adjacent column pairs.

References Cited UNITED STATES PATENTS 1,449,834- 3/ 1923 Pe'hrson 13-21 1,757,695 5/1930 Westly 13-18 1,859,979 5/1932 Miguet 13-18 2,698,777 1/1955 Hartwick et al. 13-9 2,850,554 9/1958 Friedman 13-9 X 2,993,079 7/ 1961 Augsburger 13-6 2,931,708 4/1960 Aamot 13-21 X BERNARD A. GILHEANY, Primary Examiner R. ENVALL, 1a., Assistant Examiner US. Cl. X.R. 13-10, l4, l8 

